1. Field of the Invention
The present invention relates generally to an apparatus and method of making a guidewire with a preformed three dimensional profile for use in guiding a catheter or other medical device to a desired location within a body lumen.
2. Description of the Background Art
Medical guidewires are used primarily to facilitate the placement of catheters and endoscopic instruments within the tortuous paths of body conduits. For example, if it is desirable to place a catheter within the vascular system of a patient, a guidewire is first inserted into the vessel and then guided through the tortuous path desired for the catheter. Then the catheter is threaded over the guidewire. As the catheter is advanced it tends to follow the direction of the guidewire so that it ultimately negotiates the same tortuous path. Once the catheter is in its final operative position, the guidewire can be removed leaving the catheter to perform its desired function.
Guidewires are traditionally utilized to negotiate the complex vascular system of a patient to guide a medical device, (e.g., a catheter) to a desired location. It has been in the past of paramount importance for the guidewire to have a shape which provides for superior navigation a patient""s vascular system. Inventions in the field include guidewires with floppy tips, improved methods of manufacturing, increased torqueability and improved friction reducing features to help catheters move over the guidewires. Thus the focus of the prior art has been to create a guidewire with the ability to create a path along which a catheter could follow to reach a particular site of the body.
Guidewires often use transition areas of changing diameter along their length. A smooth transition gives the guidewire the ability to better negotiate tight bends in the anatomy of the patient. The transition area of a guidewire may be long or short, that is the change from one diameter along the length of the guidewire may occur over a few millimeters, or several centimeters. In the past the use of transition areas has been combined with the use of a filament wire which covers the narrower distal section of the guidewire. The combination, well understood in the art, provides the distal tip of the wire with a greater flexibility to steer through the vasculature of a patient, while the filament wire provides added strength and radiopacity. The filament wire can also be used as a fastening point for the attachment of an atraumatic tip. Examples of guidewires using the combination of transition areas and filament wires are described in Colon et al., (U.S. Pat. No. 5,402,799) and Ashby et al., (U.S. Pat. No. 5,622,184). Others have modified the basic design by using other materials, such as Johanson et al., (U.S. Pat. No. 5,596,996). However all of the prior art to date has used guidewires for essentially the same purpose, to navigate the anatomy of a patient and direct a catheter to a particular sight within a body lumen. The medical procedure to be carried out is then conducted by the catheter. There are specialized guidewires which have been developed which attempt to do the job of a catheter using a modified guidewire. Two examples are guidewires with imaging and non-imaging sensors.
However there remains a need for a guidewire which can steer a catheter more particularly to a precise position within the vascular system of the patient. More particularly it would be beneficial to be able to manufacture a guidewire able to direct a catheter to a particular side of a lumen in the event a physician wishes to treat one side of a body lumen and not another, or be able to direct a catheter to precise locations of a body lumen. Straight guidewires are unable to perform this feat, however a novel guidewire has been disclosed in co-pending patent application Ser. No. 08/966,001 which is capable of steering catheters to a particular side of a body lumen. At least some of these objectives will be met by the embodiments of the present invention described below.
The present invention relates to medical wires, specifically guidewires and perfusion wires. In general the wires share a generally straight proximal section and a distal section having a curved three dimensional profile. The three dimensional profile usually defines a helical section having a relaxed diameter and a constrained diameter. The use of various materials and manufacturing techniques produces the variety of wires disclosed.
In a first embodiment, a guidewire for guiding another device to a desired location within a body lumen is described. The guidewire has a generally straight proximal section, and a guide section which defines a helical or other curved three dimensional profile. The three dimensional profile of the guide section is diametrically larger than the profile of the proximal section. The guide section is preferably made from a shape memory alloy and provides a curved path for another medical device to follow. The guide section has sufficient flexibility to assume a generally straight configuration when the guide section is extended through the lumen of a guiding member, such as a catheter, or is otherwise constrained.
In a second embodiment, a guidewire having a generally straight proximal section and a distal section having a helical support section is described. The helical support section defines a curved three dimensional profile that is diametrically larger than the proximal section. The helical support section is capable of elongation into a substantially straight profile when constrained and expansion into a wider diameter when unconstrained. The helical support section exerts an outward radial force (Wr) less than 20 pounds per inch, preferably less than 15 pounds per inch, usually less than 10 pounds per inch, and often less than 5 pounds per inch when axially extended so the diameter of the helical guide section is half the relaxed diameter. Exemplary ranges of outward radial force are from 0.001 pound per inch to 3 pounds per inch, usually from 0.01 pound per inch to 1 pound per inch.
In a third embodiment, a perfusion wire is disclosed with a generally straight proximal section and a distal section having a helical support section. The helical support section defines a curved three dimensional profile that is diametrically larger than the diameter of the proximal section. The helical perfusion section is capable of elongation into a substantially straight profile hen constrained and expansion to a larger diameter (Wr) when unconstrained. The helical perfusion section exerts an outward radial force in excess of 10 pounds per inch, preferably 20 pounds per inch, and often 100 pounds per inch, or higher, when axially extended so the constrained diameter is half the unconstrained diameter.
A system is described comprising a guidewire having a straight proximal section and a distal section. The distal section having a helical guide section capable of changing geometry when constrained in a lumen. The helical guide section exerts and outward radial force less than 15 pounds per inch, preferably less than 15 pounds per inch, usually less than 10 pounds per inch, and often less than 5 pounds per inch. Exemplary ranges of outward radial force are from 0.001 pound per inch to 3 pounds per inch, usually from 0.01 pound per inch to 1 pound per inch. A catheter is included in the system that is capable of tracking over the guidewire wherein the catheter is capable of following the three dimensional profile of the helical guide section. The catheter exerts an outward radial force (Peff) on a lumen at substantially the point of entry of the guidewire into the catheter, thus causing the catheter to exert an outward radial force less than 4 pounds per inch, preferably less than 2 pounds per inch, usually less than 1 pound per inch. Exemplary ranges of outward radial catheter force are from 0.0001 pound per inch to 2 pounds per inch, usually from 0.001 pound per inch to 1 pound per inch. The precise outward radial force can be determined using an equation.
The guidewire of the present invention may be manufactured using an apparatus comprising a mandrel with a heat stable core. The mandrel has at least one screw thread having spaced apart roots for receiving a guidewire. The mandrel also has at least one retainer for ensuring the guide wire is securely fixed to the mandrel. The method of using the apparatus follows the steps of wrapping a guidewire around the mandrel, securing the wire about the mandrel with the retaining device, heating the mandrel to a desired temperature, stopping the heating, cooling the mandrel and unwrapping the wire from the mandrel. A system for automating the manufacturing process is also described.
These and other embodiments are further detailed in the descriptions that follow.